Vehicular control system with synchronized communication between control units

ABSTRACT

A vehicular control system includes a first electronic control unit (ECU) and a second ECU disposed at a vehicle. The first and second ECUs are in digital communication with one another via a communication link. The first ECU transmits a first frame to the second ECU, which, responsive to receiving the first frame from the first ECU, transmits a second frame to the first ECU. The first ECU, responsive to receiving the second frame from the second ECU, determines a propagation delay based on an amount of time between when the first ECU transmitted the first frame to the second ECU and when the first ECU received the second frame from the second ECU. The first ECU, responsive to determining the propagation delay, transmits a time synchronization frame to the second ECU that is based at least in part on the determined propagation delay.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the filing benefits of U.S. provisionalapplication Ser. No. 63/199,154, filed Dec. 10, 2020, and U.S.provisional application Ser. No. 63/198,761, filed Nov. 11, 2020, whichare hereby incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to a vehicle control system fora vehicle and, more particularly, to a vehicle control system thatsynchronizes control units.

BACKGROUND OF THE INVENTION

Use of time synchronization between modules in a control system iscommon and known.

SUMMARY OF THE INVENTION

A vehicular control system includes a first electronic control unit(ECU) disposed at a vehicle equipped with the vehicular control system.The system includes a second ECU disposed at the equipped vehicle. Thefirst ECU and the second ECU are in digital communication with oneanother via a communication link. The digital communication via thecommunication link includes communication of a first frame andcommunication of a second frame. The first ECU transmits the first frameto the second ECU via the communication link. The first frame includes afirst bit pattern having a first sequence of binary digits. The secondECU, responsive to receiving the first frame from the first ECU,transmits the second frame to the first ECU via the communication link.The second frame includes a second bit pattern having a second sequenceof binary digits. The first ECU, responsive to receiving the secondframe from the second ECU, determines a propagation delay based on atime interval between (i) when the first ECU transmits the first frameto the second ECU and (ii) when the first ECU receives the second framefrom the second ECU. The first ECU transmits a time synchronizationframe to the second ECU via the communication link. The timesynchronization frame is based at least in part on the determinedpropagation delay.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a time master electronic control unit anda time slave electronic control unit exchanging bit patterns;

FIG. 2 is a table for a frame format for a synchronization message;

FIG. 3 is a schematic view of total propagation delay determination forthe time slave electronic control unit and the time master electroniccontrol unit of FIG. 1 when a switch device is used;

FIG. 4 is a diagram of time synchronization between the time masterelectronic control unit and the time slave electronic control unit ofFIG. 1; and

FIG. 5 is a block diagram for a transceiver with a timer for calculationof propagation delay.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Many vehicle systems require an accurate clock or time to properlyfunction. Thus, it is often important to accurately synchronize timebetween different vehicle systems, controllers, sensors, and/or modules.Vehicle time is commonly distributed by a master clock to a slave clockusing, for example, the precision time protocol (PTP). Timesynchronization using PTP requires two distinct communication frames(i.e., a sync frame and follow-up frame), such as two Ethernet frames,that can be sent cyclically. Precision time protocol also includesPDelay requests and PDelay responses that add additional Ethernetframes. In total, four Ethernet frames are needed to synchronize time ata slave electronic control unit (ECU) from master ECU using PTP.Implementations herein include a vehicular control system that providestime synchronization with a single Ethernet frame that includes atimestamp, thus reducing overhead for synchronization between controls.These implementations may be applied to any topology or to multi-timemaster ECUs.

In the vehicular control system described herein, a time master ECUsends a timestamp of the current time in a single Ethernet frame alongwith propagation delay corrections and back off time corrections. Areceiver and/or time slave ECU (i.e., a second ECU independent orseparate from the time master ECU) receives the single Ethernet framewith the timestamp and correction time attached to or within. Thepropagation time and back off time may be calculated by the transceiverof the time master ECU transmitting the frame using, for example, aninternal hardware timer module.

Referring now to FIG. 1, the propagation delay may be determined byfirst, after power on, linking up a time master ECU transceiver 10 and atime slave ECU transceiver 12. To establish the link, each transceiversends a pattern of pulses (i.e., logic ‘0’ signals and logic ‘1’signals) and receives back a pattern of pulses. Using these pulses, thetransceivers can negotiate a link for communication between the timemaster ECU and the time slave ECU. The amount of time required forsetting up the link may vary based on the specific Ethernettransceivers. Once the link is established, the time master ECU sends aspecial or specific bits pattern for measuring propagation delay.

For example, the Ethernet transceiver of the time master ECU sendsspecific patterns of bits, such as the binary number “1010101010101111,”that indicates the calculation for propagation delay and starts aninternal hardware timer. The Ethernet transceiver of the time slave ECUreceives the pattern of bits transmitted by the time master ECU andresponds with another specific pattern, such as the binary number“1010101011111111.” The time master ECU transceiver receives back theresponse from the time slave ECU and stops the internal hardware timerthat the time master ECU started when sending the initial specificpattern of bits. The time master ECU divides the results of the timer by2 as the timer timed both transmission and reception of the patterns.The timer measures the propagation time (Tp) with no Ethernet traffic.This time Tp should be added to every timestamp frame as the correctionor time needed for communication from one transceiver to other (i.e.,the time for a signal to propagate from one ECU to the other ECU). Thetransceiver of the time master ECU stores this Tp in a hardware register(FIG. 5) during the execution cycle. This time Tp may be added to everyoutgoing time synchronization frame.

Referring now to FIG. 2, optionally, the vehicular control systemprovides additional time corrections. For example, another useful timecorrection is when there is Ethernet traffic on a bus and the timemaster ECU is waiting for bus to be free. The Ethernet transceiver atthe time master ECU may listen on the physical medium (i.e., of the bus)to determine when the medium is free and when the time sync message mustbe transmitted. If the medium is free, the back off time is set to 0 andonly Tp is valid (i.e., the only delay is the propagation delay). TheEthernet transceiver of the time master ECU detects the timestamp framefor transmission by checking the frame type. It starts the internalhardware timer from when the physical medium is occupied until themedium is free for transmitting a frame. If the frame results in “backoff” due to a collision (i.e., two or more transceivers each sent aframe at the same time resulting in both entering back off) on thephysical medium, the timer resumes from the last point it had stopped(i.e., from the point where the frame was sent). Once the frame istransmitted, this back off time Tb is added to propagation time Tp andsent along with the frame. Thus, in this scenario, Tp+Tb (i.e., the sumof Tp and Tb) is the total propagation time for sending timestamp framesfrom time master ECU to time slave ECU. This sum results in Tc, which isthe total correction time the time slave ECU receives when receiving theframe with the timestamp (i.e., the time slave ECU adjusts the timestampby Tc).

The frame type may be a 16 bit field to indicate time sync frame. Othersized bit fields are also possible (e.g., 8 bits, 32 bits, 64 bits,etc.). The time stamp seconds may be a 32 or 64 bit field for theseconds generated on the time master ECU. The time stamp Nanoseconds maybe, for example, a 32 or 64 bit field for the nanoseconds generated onthe time master ECU. The correction time seconds may be, for example, an8 bit or 16 bit field for the correction time in seconds. Correctiontime may include the sum of propagation time (Tp) and back off time (Tb)and correction time from the previous transmission (Tpc). The correctiontime nanoseconds may be, for example, a 32 bit field for nanoseconds.The correction time includes the sum of propagation time (Tp) with backoff time (Tb) and correction time from the previous transmission (Tpc).

Referring now to FIG. 3, optionally, when there are multiple devices inbetween the time master ECU and the time slave ECU (i.e., intermediarydevices), the correction time is added accordingly. Both the timestamp(i.e., the propagation delay Tp and the back off delay Tb) and Tc shouldgenerally be considered for synchronization time. The total correctiontime Tc may be the time sent by a previous master switch device 14(i.e., Tsw) which receives frames from the time master ECU and forwardsthe frames to the time slave ECU. For each connection of ECUs, the timeTc is calculated by the same method as described above. Additionally,the time correction from the previous link (Tpc) is added to current theTc to have an accurate correction in time.

Referring now to FIG. 4, an example for synchronizing time from timemaster to time slave ECU is illustrated. In this example, the timemaster ECU begins synchronizing when a time value is equal to 100seconds. After the initial link establishment, propagation time ismeasured as Tp=1 second. This time is added for every synchronizationrequest from master along with back off time (Tb). In the firstsynchronization request, Tb=1 second. Thus, the time slave ECU receivestime=100 seconds+2 seconds=102 seconds. The slave ECU synchronizes tothe time 102 seconds based on the correction sent with the timestamp.During the second synchronization request, at a time value of 104seconds (i.e., 4 seconds after the initial starting time value of 100seconds), at the time master ECU, Tc=3s. Thus, the time slave ECUsynchronizes to 107 seconds. Thus, the time master and the time slaveECUs are synchronized accurately with a common time.

Ingress timestamp and egress timestamp corrections may not be consideredin the timestamp fields in the frame format. The time should becorrected to the exact point in time at the time master ECU when theframe is assembled in the Ethernet MAC descriptor and is ready fortransmission. In the case when the packets are queued in the descriptorchain, the final time should be used when the frame is transmitted fromthe Ethernet controller (MAC) to the Ethernet transceiver (TRCV) toachieve exact time synchronization. Similarly, the time slave ECUimplements correction in time from the received frame until theprocessing of the synchronization frame. This correction is added to thesynchronized time for increased accuracy.

Referring now to FIG. 5, the block diagram 500 of the transceiver 510includes a propagation time control block that controls the sending andreceiving of the specific bit patterns for measuring the propagationdelay. The propagation time control may also access the internalhardware timer to start the timer, stop the timer, and access registervalues. A back off time control block controls the internal hardwaretimer when a back off is detected on the physical medium. The back offtime control may also access the internal hardware timer to start thetimer, stop the timer, and copy values. The internal hardware timer maybe a free running timer. A register to store Tp, a register to store Tb,and a register to store Tpc are each registers that store Tp, Tb, andTpc respectively (i.e., store the respective times). The “Calculate Tc”block consolidates all of the stored times (i.e., Tp, Tb, and Tpc)together and updates, in the time synchronization frame, for fieldcorrection time Tc.

Thus, the vehicular control system allows for a time master ECU tosynchronize time with other ECUs with a single Ethernet frame thatincludes a timestamp. The single Ethernet frame includes a correctiontime for achieving synchronization with reduced traffic on time syncframes. In conventional time sync methods using PTP, sync and follow-upmessages are configured for 125 ms and PDelay requests and responses for1 second. In this case, 18 frames per second are needed for timesynchronization. This adds additional traffic on the Ethernet bus.However, this additional traffic is greatly reduced by the vehicularcontrol system described herein. For example, as opposed to 18 framesper second, the vehicular control system can be used in such a way thatsync requests (of a single Ethernet frame) are sent every 125 ms usingonly low-level hardware (i.e., within the transceiver). This exampleresults in 8 frames per second which is a reduction of greater than 50percent. Because the transceiver sends/recognizes the bit patterns(i.e., the binary sequence of ‘1’s and ‘0’s) within the hardware of thetransceiver, the system allows for rapid and accurate propagation delaythat does not incur the overhead costs and delays of softwareprocessing. Because the amount of Ethernet traffic used by theautomotive industry is increasing rapidly, the bandwidth on the Ethernetbus is becoming a notable problem between communication partners. Thus,the bandwidth reductions achieved by the vehicular control system areadvantageous.

In conventional Ethernet systems, propagation delay is calculated withtransmission of multiple Ethernet frames with pdelay request and pdelayresponse frames. Software is then used to calculate the propagationdelay. In contrast, implementations herein include a system thatdetermines propagation delay using Ethernet transceiver hardware (asopposed to software) and a single Ethernet frame (as opposed to multipleEthernet frames). The system uses bit pattern exchanges from onetransceiver to another to measure propagation delay. The Ethernettransceivers can send propagation delays for each transmitted Ethernetframe in the frame itself. Propagation delay between the communicationpartners is thus calculated in the same Ethernet frame instead of atraditional request/response format.

The ECU, such as the master ECU and/or slave ECU (i.e., a first ECUand/or a second ECU), may be part of a driving assist system of thevehicle. For example, one or both of the ECUs may generate a respectiveoutput for one or more driving assist systems of the vehicle, such asfor an object detection system of the vehicle, a collision avoidancesystem of the vehicle, a pedestrian detection system of the vehicle, aheadlamp control system of the vehicle, a lane departure warning systemof the vehicle, a lane keep assist system of the vehicle, an adaptivecruise control system of the vehicle, and/or an automatic emergencybraking system of the vehicle. The output or outputs may at least inpart control one or more of the driving assist systems or one or morefunctions or operations of the vehicle. For example, the master or firstor control ECU may be disposed in the vehicle and the slave or secondECU may be part of a camera or sensor or sensing system of the vehicle,and the synchronized outputs of the ECUs may control or provide outputsfor one or more of the driving assist systems (e.g., automatic breakingsystems, lane keep systems, lane centering systems, adaptive cruisecontrol systems, etc.) of the vehicle.

The vehicle may include any type of sensor or sensors, such as imagingsensors or radar sensors or lidar sensors or ultrasonic sensors or thelike. The imaging sensor or camera may capture image data for imageprocessing and may comprise any suitable camera or sensing device, suchas, for example, a two dimensional array of a plurality of photosensorelements arranged in at least 640 columns and 480 rows (at least a640×480 imaging array, such as a megapixel imaging array or the like),with a respective lens focusing images onto respective portions of thearray. The photosensor array may comprise a plurality of photosensorelements arranged in a photosensor array having rows and columns. Theimaging array may comprise a CMOS imaging array having at least 300,000photosensor elements or pixels, preferably at least 500,000 photosensorelements or pixels and more preferably at least 1 million photosensorelements or pixels arranged in rows and columns. The imaging array maycapture color image data, such as via spectral filtering at the array,such as via an RGB (red, green and blue) filter or via a red/redcomplement filter or such as via an RCC (red, clear, clear) filter orthe like. The logic and control circuit of the imaging sensor mayfunction in any known manner, and the image processing and algorithmicprocessing may comprise any suitable means for processing the imagesand/or image data.

For example, the vision system and/or processing and/or camera and/orcircuitry may utilize aspects described in U.S. Pat. Nos. 9,233,641;9,146,898; 9,174,574; 9,090,234; 9,077,098; 8,818,042; 8,886,401;9,077,962; 9,068,390; 9,140,789; 9,092,986; 9,205,776; 8,917,169;8,694,224; 7,005,974; 5,760,962; 5,877,897; 5,796,094; 5,949,331;6,222,447; 6,302,545; 6,396,397; 6,498,620; 6,523,964; 6,611,202;6,201,642; 6,690,268; 6,717,610; 6,757,109; 6,802,617; 6,806,452;6,822,563; 6,891,563; 6,946,978; 7,859,565; 5,550,677; 5,670,935;6,636,258; 7,145,519; 7,161,616; 7,230,640; 7,248,283; 7,295,229;7,301,466; 7,592,928; 7,881,496; 7,720,580; 7,038,577; 6,882,287;5,929,786 and/or 5,786,772, and/or U.S. Publication Nos.US-2014-0340510; US-2014-0313339; US-2014-0347486; US-2014-0320658;US-2014-0336876; US-2014-0307095; US-2014-0327774; US-2014-0327772;US-2014-0320636; US-2014-0293057; US-2014-0309884; US-2014-0226012;US-2014-0293042; US-2014-0218535; US-2014-0218535; US-2014-0247354;US-2014-0247355; US-2014-0247352; US-2014-0232869; US-2014-0211009;US-2014-0160276; US-2014-0168437; US-2014-0168415; US-2014-0160291;US-2014-0152825; US-2014-0139676; US-2014-0138140; US-2014-0104426;US-2014-0098229; US-2014-0085472; US-2014-0067206; US-2014-0049646;US-2014-0052340; US-2014-0025240; US-2014-0028852; US-2014-005907;US-2013-0314503; US-2013-0298866; US-2013-0222593; US-2013-0300869;US-2013-0278769; US-2013-0258077; US-2013-0258077; US-2013-0242099;US-2013-0215271; US-2013-0141578 and/or US-2013-0002873, which are allhereby incorporated herein by reference in their entireties. The systemmay communicate with other communication systems via any suitable means,such as by utilizing aspects of the systems described in U.S. Pat. Nos.10,071,687; 9,900,490; 9,126,525 and/or 9,036,026, which are herebyincorporated herein by reference in their entireties.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the invention,which is intended to be limited only by the scope of the appendedclaims, as interpreted according to the principles of patent lawincluding the doctrine of equivalents.

1. A vehicular control system, the vehicular control system comprising:a first electronic control unit (ECU) disposed at a vehicle equippedwith the vehicular control system; a second ECU disposed at the equippedvehicle; wherein the first ECU and the second ECU are in digitalcommunication with one another via a communication link, wherein thedigital communication via the communication link comprises communicationof a first frame and communication of a second frame; wherein the firstECU transmits the first frame to the second ECU via the communicationlink, wherein the first frame comprises a first bit pattern having afirst sequence of binary digits; wherein the second ECU, responsive toreceiving the first frame from the first ECU, transmits the second frameto the first ECU via the communication link, wherein the second framecomprises a second bit pattern having a second sequence of binarydigits; wherein the first ECU, responsive to receiving the second framefrom the second ECU, determines a propagation delay based on a timeinterval between (i) when the first ECU transmits the first frame to thesecond ECU and (ii) when the first ECU receives the second frame fromthe second ECU; and wherein the first ECU transmits a timesynchronization frame to the second ECU via the communication link, andwherein the time synchronization frame is based at least in part on thedetermined propagation delay.
 2. The vehicular control system of claim1, wherein the first ECU comprises a first transceiver and the secondECU comprises a second transceiver, and wherein the first frame istransmitted by the first transceiver and received by the secondtransceiver and the second frame is transmitted by the secondtransceiver and received by the first transceiver.
 3. The vehicularcontrol system of claim 1, wherein the first frame indicates to thesecond ECU an intent to determine the propagation delay between thefirst ECU and the second ECU.
 4. The vehicular control system of claim1, wherein the first ECU determines the propagation delay based on atimer that (i) is started when the first ECU transmits the first frameto the second ECU and (ii) is terminated when the first ECU receives thesecond frame from the second ECU.
 5. The vehicular control system ofclaim 4, wherein the first ECU determines the propagation delay bydividing a result of the timer by two.
 6. The vehicular control systemof claim 4, wherein the timer is an internal hardware timer.
 7. Thevehicular control system of claim 1, wherein the first ECU determines aback off time delay, and wherein the time synchronization framecomprises the back off time delay.
 8. The vehicular control system ofclaim 7, wherein the time synchronization frame comprises a totalpropagation delay which comprises a sum of the propagation delay and theback off time delay.
 9. The vehicular control system of claim 1, whereinthe first bit pattern is different from the second bit pattern.
 10. Thevehicular control system of claim 1, wherein the time synchronizationframe comprises a timestamp indicative of a point in time when the framesynchronization frame is transmitted by the first ECU.
 11. The vehicularcontrol system of claim 1, further comprising a switch, wherein thefirst ECU transmits the time synchronization frame to the second ECU viathe switch, and wherein the switch transmits the time synchronizationframe to the second ECU with a switch propagation delay summed with thepropagation delay.
 12. The vehicular control system of claim 1, whereinthe communication link comprises an Ethernet communication link.
 13. Thevehicular control system of claim 1, wherein the first ECU stores thedetermined propagation delay.
 14. The vehicular control system of claim1, wherein the first ECU is part of a driving assist system of thevehicle.
 15. A vehicular control system, the vehicular control systemcomprising: a first electronic control unit (ECU) disposed at a vehicleequipped with the vehicular control system; a second ECU disposed at theequipped vehicle; wherein the first ECU and the second ECU are indigital communication with one another via a communication link; whereinthe first ECU transmits, to the second ECU via the communication link, afirst bit pattern having a first sequence of binary digits; wherein thesecond ECU, responsive to receiving the first bit pattern from the firstECU, transmits, to the first ECU via the communication link, a secondbit pattern having a second sequence of binary digits; wherein the firstECU, responsive to receiving the second bit pattern from the second ECU,determines a propagation delay based on a time interval between (i) whenthe first ECU transmits the first bit pattern to the second ECU and (ii)when the first ECU receives the second bit pattern from the second ECU;and wherein the first ECU transmits a time synchronization frame to thesecond ECU via the communication link, and wherein the timesynchronization frame is comprises a timestamp and a correction time,and wherein the correction time is based at least in part on thedetermined propagation delay.
 16. The vehicular control system of claim15, wherein the first and second ECUs communicate Ethernet frames viathe communication link, and wherein a first Ethernet frame communicatedby the first ECU via the communication link comprises the first bitpattern and a second Ethernet frame communicated by the second ECU viathe communication link comprises the second bit pattern.
 17. Thevehicular control system of claim 15, wherein the first ECU comprises afirst transceiver and the second ECU comprises a second transceiver, andwherein the first bit pattern is transmitted by the first transceiverand received by the second transceiver and the second bit pattern istransmitted by the second transceiver and received by the firsttransceiver.
 18. The vehicular control system of claim 15, wherein thefirst bit pattern indicates to the second ECU an intent to determine thepropagation delay between the first ECU and the second ECU.
 19. Avehicular control system, the vehicular control system comprising: afirst electronic control unit (ECU) disposed at a vehicle equipped withthe vehicular control system; a second ECU disposed at the equippedvehicle, wherein the second ECU generates a first output for at leastone driving assist system of the equipped vehicle; wherein the first ECUand the second ECU are in digital communication with one another via anEthernet communication link, wherein the digital communication via theEthernet communication link comprises communication of a first frame andcommunication of a second frame; wherein the first ECU transmits thefirst frame to the second ECU via the Ethernet communication link,wherein the first frame comprises a first bit pattern having a firstsequence of binary digits; wherein the second ECU, responsive toreceiving the first frame from the first ECU, transmits the second frameto the first ECU via the Ethernet communication link, wherein the secondframe comprises a second bit pattern having a second sequence of binarydigits; wherein the first ECU, responsive to receiving the second framefrom the second ECU, determines a propagation delay based on a timeinterval between (i) when the first ECU transmits the first frame to thesecond ECU and (ii) when the first ECU receives the second frame fromthe second ECU; wherein the first ECU transmits a time synchronizationframe to the second ECU via the Ethernet communication link, and whereinthe time synchronization frame is based at least in part on thedetermined propagation delay; and wherein the second ECU, at leastpartially responsive to receiving the time synchronization frame,generates a second output for the at least one driving assist system ofthe equipped vehicle.
 20. The vehicular control system of claim 19,wherein the first ECU determines the propagation delay based on a timerthat (i) is started when the first ECU transmits the first frame to thesecond ECU and (ii) is terminated when the first ECU receives the secondframe from the second ECU.
 21. The vehicular control system of claim 20,wherein the first ECU determines the propagation delay by dividing aresult of the timer by two.
 22. The vehicular control system of claim20, wherein the timer is an internal hardware timer.